I'm not 100% across Chinese politics, but from what I understand the Politburo[1] (where the top leaders sit, including Xi) are voted in by the Central Committee [1].
But the Central Committee isn't really an independent body, and the people who sit there are selected by the Politburo - effectively the Politburo members just vote themselves in.
(P.s. as mentioned I'm not 100% across the politics in China so happy to be corrected)
Is there not some sort of democratic structure that allows people to have a say in their government? If you took a survey of random Chinese people would they say Xi Xinping is some dictator that they don't want there?